The invention relates to magnetic recording heads, and more particularly, to a low moment material for forming a hybrid write pole of a perpendicular magnetic recording head.
Magnetic recording heads have utility for use in a magnetic disc drive storage system. Most magnetic recording heads used in such systems today are xe2x80x9clongitudinalxe2x80x9d magnetic recording heads. Longitudinal magnetic recording in its conventional form has been projected to suffer from superparamagnetic instabilities at densities above approximately 40 Gbit/in2. It is believed that reducing or changing the bit cell aspect ratio will extend this limit up to approximately 100 Gbit/in2. However, for recording densities above 100 Gbit/in2, different approaches will likely be necessary to overcome the limitations of longitudinal magnetic recording.
An alternative to longitudinal recording is xe2x80x9cperpendicularxe2x80x9d magnetic recording. Perpendicular magnetic recording is believed to have the capability of extending recording densities well beyond the limits of longitudinal magnetic recording. Perpendicular magnetic recording heads for use with a perpendicular magnetic storage medium may include a pair of magnetically coupled poles, including a main write pole having a relatively small bottom surface area and a flux return pole having a larger bottom surface area. A coil having a plurality of turns is located adjacent to the main write pole for inducing a magnetic field between that pole and a soft underlayer of the storage media. The soft underlayer is located below the hard magnetic recording layer of the storage media and enhances the amplitude of the field produced by the main pole. This, in turn, allows the use of storage media with higher coercive force, consequently, more stable bits can be stored in the media. In the recording process, an electrical current in the coil energizes the main pole, which produces a magnetic field. The image of this field is produced in the soft underlayer to enhance the field strength produced in the magnetic media. The flux density that diverges from the tip into the soft underlayer returns through the return flux pole. The return pole is located sufficiently far apart from the main write pole such that the material of the return pole does not affect the magnetic flux of the main write pole, which is directed vertically into the hard layer and the soft underlayer of the storage media.
A magnetic recording system such as, for example, a perpendicular magnetic recording system may utilize a write pole having uniform magnetic properties, i.e. the write pole is formed of a single material having a uniform magnetic moment. However, such a write pole can exhibit skew effects which can degrade adjacent tracks.
Such magnetic recording systems alternatively may utilize a write pole having a xe2x80x9chybridxe2x80x9d design wherein, for example, a high saturation magnetic moment material is formed on top of or adjacent to a low saturation magnetic moment material. This type of design has been found effective in, for example, reducing skew effects during the writing process.
In constructing the hybrid write pole, the high moment material and the low moment material must be coupled, for example by exchange coupling, and together they should satisfy all magnetic requirements of a standard write pole such as, for example, soft and uniaxial magnetic properties and a relatively low hard axis remanence (Mrh). Specifically, the soft and uniaxial magnetic properties contribute to an efficient writer, while a low Mrh reduces or eliminates writing when the head is not energized.
For the write pole design, most of the focus has been on developing high moment materials having suitable properties, such as a relatively large saturation magnetization (4 xcfx80 Ms), a low coercivity and a generally well defined uniaxial anisotropy. These factors are important for the write pole and in particular for a perpendicular magnetic recording head which utilizes a deep gap field to perform a write operation as opposed to a fringing field utilized by a longitudinal magnetic recording head. However, with the development of the hybrid pole design, there is an increased focus on low moment materials which have a unique property set and characteristics as well. For example, the low moment material should have magnetically soft and uniaxial properties for head efficiency, a relatively low saturation magnetization or moment to reduce or eliminate writing when the head is not energized and a relatively high resistivity to reduce eddy current losses.
Accordingly, there is identified a need for an improved magnetic recording head that overcomes limitations, disadvantages, and/or shortcomings of known magnetic recording heads. In addition, there is identified a need for improved low saturation magnetization or low moment materials for use in forming a write pole, and particularly a hybrid main write pole, of a perpendicular magnetic recording head that overcomes limitations, disadvantages, and/or shortcomings of known write poles.
Embodiments of the invention meet the identified needs, as well as other needs, as will be more fully understood following a review of the specification and drawings.
In accordance with an aspect of the invention, a main write pole for a perpendicular magnetic recording head comprises a first layer of material having a saturation magnetic moment less than about 1.0 T and a second layer of material adjacent the first layer and having a saturation magnetic moment greater than the saturation magnetic moment of the first layer of material. The first layer of material may be formed of NiFe alloys. More specifically, the first layer of material may be formed of NiFeX, wherein X comprises Cr, Cu, and/or Ti. More specifically, the first layer of material may be formed of (NiFe)100xe2x88x92yXy, wherein X comprises Cr, Cu and/or Ti and wherein y is in the range of about 2 to about 50.
In accordance with an additional aspect of the invention, a main write pole for a perpendicular magnetic recording head comprises a first layer of material having a first saturation magnetic moment and a second layer of material adjacent the first layer and having a second saturation magnetic moment that is greater than the first saturation magnetic moment. The first layer of material may include (NiFe)100xe2x88x92yXy, wherein X comprises Cr, Cu and/or Ti and wherein y is in the range of about 2 to about 50.
In accordance with another aspect of the invention, a magnetic disc drive storage system comprises a magnetic recording medium and a magnetic recording head positioned adjacent the magnetic recording medium. The magnetic recording head includes a write pole which comprises a first layer of material having a saturation magnetic moment less than about 0.5 T and a second layer of material adjacent the first layer and having a saturation magnetic moment greater than the saturation magnetic moment of the first layer of material.